Pine Tar; History And Uses

Theodore P. Kaye
Few visitors to any ship which as been rigged in a traditional manner
have left the vessel without experiencing the aroma of pine tar. The aroma
produces reactions that are as strong as the scent; few people are ambivalent
about its distinctive smell. As professionals engaged in the restoration
and maintenance of old ships, we should know not only about this product,
but also some of its history.

Wood tar has been used by mariners as a preservative for wood and rigging
for at least the past six centuries. In the northern parts of Scandinavia,
small land owners produced wood tar as a cash crop. This tar was traded
for staples and made its way to larger towns and cities for further distribution.
In Sweden, it was called "Peasant Tar" or was named for the district from
which it came, for example, Lukea Tar or Umea Tar.

At first barrels were exported directly from the regions in which they
were produced with the region's name burned into the barrel. These regional
tars varied in quality and in the type of barrel used to transport it to
market. Wood tars from Finland and Russia were seen as inferior to even
the lowest grade of Swedish tar which was Haparanda tar.

In 1648, the newly formed NorrlSndska TjSrkompaniet (The Wood Tar Company
of North Sweden) was granted sole export privileges for the country by
the King of Sweden. As Stockholm grew in importance, pine tar trading concentrated
at this port and all the barrels were marked "Stockholm Tar". By 1900,
NorrlSndska TjSrkompaniet had lost its control of the pine tar export business,
and other exporters were again working out of other ports and marking their
product accordingly. Nevertheless, over the centuries "Stockholm Tar" has
come to mean a high quality light colored wood tar.

Gamble1 describes one of the earliest Swedish methods of
making tar in Norrland (Northern Sweden). The peasants dug up and cleaned
the roots of Swedish pine trees (Pinus silvestris) in the late summer.
They then transported the roots to the burn site where they were split
and stacked to weather during the winter.

" The 'dale' or burning ground, was built of logs in a scientific manner.
It was built on a slope which sometimes forms one side, in the shape of
a funnel, with a spout at the lower end of the slope. The outer walls of
the 'dale' were built with logs split in two, and a layer of earth was
then placed thereon before the interior was lined, either with clay, iron
sheet, or thick cardboard."2

In the summer, the split roots or fatwood were stacked in the kiln and
covered with peat and turf. Brush wood was used to provide heat, but the
heat was controlled so that the remaining fibers were not burned and the
roots give up their liquid. This tar was high in turpentine and was in
great demand.3 By the turn of the 20th century , this traditional
way competed with more modern methods of production. Although it produced
higher quality tar, it was labor intensive and could not be competitive
in the world market.

From the beginning, Britain's colonies in North American were encouraged
to produce pine tar and pitch, and to collect gum from pine trees for later
shipment to England. These fledgling industries in New England and the
Carolinas were encouraged by the Bounty Act of 1705. At that time England
had been cut off from its Scandinavian supplies by Russia's invasion of
Sweden-Finland. " By 1725 four fifths of the tar and pitch used in England
came from the American colonies..."4 This supply remained constant
until the American Revolution in 1776, when England was again forced to
trade with the Dutch for Scandinavian products. As the population of the
United States grew and moved west, forests were cleared. The southern states
began to monopolize the production, because of the type of trees in this
reagon. By 1850 most of the U.S. production of tar and pitch was in North
and South Carolina. As the 19th Century progressed the tar, pitch, and
turpentine manufacturing spread south and west into the states of Georgia,
Alabama, Mississippi, Louisiana, Texas, and Florida. By 1900, rosin and
turpentine were the dominant products, and the states of Georgia, Florida,
and Alabama were the three major producers.5

As the maritime uses of pine tar deminished over the latter half of
the 19th century so did its production in the U.S. During this time technological
advances had taken place which made it possible to produce tar, but as
a by product. The process of destructive distillation was incorporated
to manufacture soft wood charcoal and the by products of pine tar in kilns
using Long-leaf or Cuban pine.6 These kilns or retorts "...
varied in capacity from one to ten cords. They were usually horizontal,
cylindrical, steel vessels set in brickwork, with the fire box at one or
both ends, and are charged and discharged at one or both ends. ...By this
plan fat wood is piled in a pit or brick kiln, so arranged that the tar,
when formed, runs to a point where it may be collected, and dipped into
barrels."7 The term " fat wood" or "light wood"8
refers to yellow pine that is devoid of its bark and growth wood. Prior
to the mid-twentieth century, stumps and blow downs were used to make this
type of product because of their relative low cost. "If a pit is used,
the wood is covered with earth, and if a brick kiln this is closed nearly
air tight and the wood burned very slowly until charred. In this process
nothing is recovered but tar and charcoal."9

Many different heat sources were used to produce distillation. At some
works gasses and oils were collected from the top of the kiln and run through
a condenser to produce "wood turpentine" and "pine oil". The average yield
for one cord (4,000 lb.) of "light wood" might be:

Wood turpentine

8 to 15 gal.

Total oils; including tar

65 to 100 gal

Tar

40 to 60 gal.

Charcoal

25 to 35 bushels or 403 to 564 lbs.10

Because of its strong odor, wood turpentine was used as a substitute for
second grade gum turpentine in exterior paints and varnishes. Tar and tar
oils were added to paints, stains, disinfectants, soaps, and floating oils.
The oakum and cordage industry used the majority of the pine tar produced.

At Mystic Seaport Museum pine tar is used for protective coatings on
both cordage, oakum, and wood. Standing rigging is inspected regularly
and replaced when necessary. When it is wormed, parceled, and server; a
mixture of pine tar and varnish11 is used between the layers
to protect the natural fibers, and a final coating is applied which will
become hard and shiny when dry. We have also had success re-tarring oakum
which has partially dried out.

"Our intent was to create a solution that would be absorbed into the
fibers of the oakum in order to preserve the fibers. The mixture also had
to be able to dry out sufficiently in the open air and not be "sticky"
to the touch.

To a quart of pine tar, add approximately one gallon of paint thinner
(we used 'Thin-X' by SCL Sterling Corp. '100% mineral spirits') or more,
and thoroughly mix until the tar is good and thin. Into a 5 gallon metal
pail, the thinned pine tar was mixed with turpentine - enough added to
fill the pail.12"

The Museum's use of pine tar as a wood preservative is limited. A soaking
oil of turpentine,13 boiled linseed oil, pine tar, and Japan
dryer14 is used on some work boats and collection vessels. This
mixture has been called "Old Down East Deck Coating" by some people. A
variation of this coating for a wood preservative below ground eliminates
the Japan dryer, and the other three ingredients are of equal measure by
volume.

For at least the past decade, we have been purchasing pine tar from
Natrochem in Savannah, Georgia. Natrochem's supplier is Auson Chemical
Industry, Gsteborg, Sweden. We learned from Auson that they make many grades
of pine tar for many different uses, but the product exported to the U.S.
is EU-588 15 (Natrotar 588), and is a "so-called old fashioned
type of tar", and is a byproduct of soft wood charcoal production.16
Today, Auson makes tar mostly from ordinary pine wood, and controls the
amount of phenolic substances (pitch, water, acetic acid, and impurities
such as soot and cellulose) by using vacuum distillation which operates
at a temperature range of 175-2800 C. Soft wood tars contain resinous,
fatty, terpenic ingredients which, when applied on wood, allow the wood
to breathe and not rot from within. 17 Auson also receives every
year limited quantities of "peasant tar"18 produced in old fashioned
dales. In Sweden, this tar is twice the price of the next lower grade,
and it is not usually exported due to the domestic demand.

The continuation of pine tar in the American market place is not dependent
on its maritime uses. If it were not for soaps, shampoos, veterinary medicines,
and tree limb treatments there would not be enough of a demand for Natrochem
to import pine tar in bulk just for maritime uses. Many products which
were used only for the repair and maintenance of vessels have been lost
forever because the demand for them is not sufficient to keep them in the
marketplace. We can only try to support , through use, products that we
feel are essential to our field.

APPENDIX

All information in this appendix has been supplied by Auson AB, Goteborg
, Sweden

Wood Tar - Pine Tar General

Wood Tar is a viscous, blackish brown liquid, translucent in thin layers.
It has an empyreumatic odor and sharp taste. The chief constituents are
volatile terpene oils, neutral oils of high boiling point and high solvency,
resin and fatty acids. The proportion of these vary in the different grades
of tar, also according to tree species and the part of the tree used, type
of carbonization oven ect.... Fat wood tar made from stumps of the pine
tree has always been recognized as the best tar, since it contains much
of the ingredients which protect the living tree. However, stumps are hard
to find and expensive, so ordinary pine wood is mostly used nowadays.

Genuine Pine Tar 588

General: A dark colored, old fashion type of pine tar obtained
as a byproduct through destructive distillation of pine wood in the manufacture
of charcoal. Thinned with turpentine to a standard viscosity.

Technical data

Density at 20oC

1.05

Water content:

max. 0.5%

Volatile matter

max. 6.0%

Ash content:

max. 0.5%

Viscosity at 50o C

approx. 380 cP

Acidity (as acetic acid)

max. 0.3%

Flash point:

approx. 120oC

Thinner:

Turpentine

Kiln burned Pine Tar 773

General: Golden brown pine tar produced according to the old
kiln method from stumps of the pine tree Pinus Silvestris,. Also known
as "peasant made" tar. This type of tar is characterized by high resin
content ( rosin acids and retene), low content of pitch and high purity,
i.e. free from soot and other impurities.

Technical data:

Density at 20oC

approx. 1.05

pH value:

approx. 3.5

Reaction with Ca (OH)2

positive

Water content:

approx. 1%

Solubility:

soluble in ethanol, ether and in fixed and volatile oils; slightly
soluble in water